CTU president Karen Lewis stepping down

CHICAGO (AP) - Chicago Teachers Union president Karen Lewis says she is stepping down because her battle with brain cancer has made it impossible to do her job "at my best."

Lewis said Friday that she's submitted her retirement papers to the Chicago Board of Education.

Lewis was diagnosed with brain cancer four years ago, has undergone chemotherapy, suffered a stroke, and underwent brain surgery recently.

In her eight years as union president, Lewis has been a fiery leader who has been engaged with an ongoing war-of-words with Mayor Rahm Emanuel. In 2012 she led a seven-day strike -- the first such work stoppage for the union in a quarter century.

She called off a widely expected run for mayor against Emanuel when she was diagnosed with cancer.